Stirrer, multiple

The membrane preparation is diluted to an appropriate final concentration in the incubation buffer and the mixture is stirred with a magnetic stirrer. Because multiple aliquots will be taken from the incubation mixture, it is important to start with an adequate total volume. To initiate association, the radioligand is added to the mixture under constant stirring. 

High conversion, similar to that in a tubular reactor with multiple feed, is obtained in a multi-chamber or multi-zone autoclave reactor. This is an elongated cylindrical vessel with a ratio of length to inner diameter of 10 - 12. It is subdivided by baffles and the stirrer into two to five chambers (Fig. 5.1-8, left). 

Thermometers. The sensor probe should be placed in the bath in a central location removed from the heater and stirrer units. If a single cell or sample holder immersed in the bath is the only object of interest, the probe should be placed near this cell but not touching it. The measuring thermometer should be placed in good thermal contact with the cell or sample holder if there is only one or positioned close to the location of multiple cells. 

Modern reactors are made of stainless steel and have capacities up to as much as 180 m (50,000 U.S. gal.). Designs vary, and include top and bottom entry stirrers and multiple impellers. Agitation of the reaction mixture must be given serious attention since many monomers are less dense than water while their polymers are more dense. The mixing systems must then pull monomer down from the surface of the charge and lift polymer olT the floor of the reaction vessel. 

The reaction is conducted in a 250-mL, three-necked flask, fitted with a mechanical stirrer, a thermometer reaching close to the bottom of the flask, and a 25-cm Vigreux column to which has been connected a distillation head with multiple receiver. tert-Butyldichlorophosphine (31.8 g, 0.2 mole) is added to a stirred suspension of NaF (25.2 g, 0.6 mole) in 100 mL of sulfolane over a period of 1 hour. A slow stream of nitrogen is passed through a T-tube connected to the outlet of the distillation apparatus. After the addition of the chloro-phosphine, the reaction mixture is heated as follows 45 minutes at 80°, 15 minutes at 100-180°, and 30 minutes at 180°. Distillation of the fluorophosphine commences at 80° and is complete at 180°. The product is collected in a receiver flask cooled in Dry Ice. fer -Butyldifluorophosphine is obtained as a colorless liquid of bp 41-44° the yield is 20-23 g (79-91%, based on tert-butyl-dichlorophosphine ). Anal. Calcd. for C4H9F2P P, 24.6 F, 30.2. Found P, 24.1 F, 29.0,... 

The all-glass reactor consisted of two detachable parts. The upper part was equipped widi four necks for fitting the two inlet tubes, a thermometer, and a powerful multiple-blade stirrer. The lower part of the reactor was immersed in a constant temperature bath, equipped with both heaters and cooling coils. The temperature bath was controlled by a J-tube type thermostat sensitive to 0.1° C. 

In multiple hearth roasters, which have up to 15 hearths, the pulverized material is agitated with a stirrer arm and is transported from one hearth to another, thereby continuously renewing the surface of the ore being calcined. The roasting gases leave the furnace with 9 to 12% by volume of sulfur dioxide at 700 to 750°C. They are cooled over a waste heat boiler, in which steam is produced. 

Most experimental kinetic curves are rather smooth, i.e, the concentration of adsorbate in solution monotonically decreases, but some kinetic curves reported in the literature have multiple minima and maxima, which are rather unlikely to be reproducible. Such minima and maxima represent probably the scatter of results due to insufficient control over the experimental conditions. For instance use of a specific type of shaker or stirrer at constant speed and amplitude does not necessarily assure reproducible conditions of mass transfer. Some publications report only kinetic data—results of experiments aimed merely at establishing the sufficient equilibration time in equilibrium experiments. Other authors studied adherence of the experimentally observed kinetic behavior to theoretical kinetic equations derived from different models describing the transport of the adsorbate. Design of a kinetic experiment aimed at testing kinetic models is much more demanding, and full control over all parameters that potentially affect the sorption kinetics is hardly possible. 

Furthermore, it is evident that the power input P0 9, particularly in the laminar range, is a multiple of that from the power balance in equation (5.35) based on equating the thrust and sinking powers. Further, the factor of 3 difference in power input between the two stirrer types should be noted, see the comments in Section... 

As physical destruction of the polymer matrix by stirring might deactivate the catalyst, an automatic shaker instead of a magnetic stirrer was utilized, allowing preservation of the catalyst activity, even after multiple use, to afford the homoallylic alcohol in high yields (1st cycle 90% yield, 2nd cycle 86% yield, 3rd cycle 86% yield). 

To overcome the weaknesses of the column fermenter, alternatives have been proposed. A tapered column fermenter can maintain a high airflow rate at the lower section of the fermenter where the cell concentration is high. Several sieve plates can be installed in the column for the effective gas-liquid contact and the breakup of the coalesced bubbles. The cylindrical column can be divided into multiple stages with stirrers. This configuration is analogous to stirred-tank fermenters connected in series. To enhance the mixing, the fermentation broth can be recirculated by using a pump. 

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